1. Field of the Invention
The present invention generally relates to an optical deflecting device changing a reflection direction of an incident light flux, and a method for driving the optical deflecting device, and for example relates to a technology suitable for use in an image forming apparatus of electrophotography, such as a printer, a copier, etc., and a projection-type image and video display apparatus, such as a projector, a digital theater system, etc.
2. Discussion of the Background
A digital micromirror device using a torsion-beam hinge has been proposed by L. J. Hornbeck (see “1989 Proc. SPIE Vol. 1150, pp 86-102”), and a space optical modulation device having a micromirror group, evolved from the technology of the digital micromirror device called a DMD (Digital Micromirror Device), is used in an image projection apparatus (see “1998 Proc. of the IEEE, vol. 86, No. 8, pp 1687-1704”).
In these devices, generally, a mirror is supported with a torsion beam called a hinge, and the reflective area of the mirror is decreased because of using the hinge. However, in the above-described DMD, a reflection member is provided to a surface of the mirror separately from a hinge part, in a bi-level structure. Further, although the actual drive voltage becomes a several dozen volt because of using the hinge, to control the data for switching the inclination direction of the mirror with about 5-7.5V, switching of the inclination direction of the mirror is performed by combining a biasing voltage of several dozen volt, which is added to a plurality of DMDs, each constituting a pixel, all at one time, and a restoring force of a special spring member.
Further, an optical deflecting device in which a plate-like member having a light reflective area does not have a fixed end such as a hinge has been proposed, for example, in Japanese Patent Application Laid-open Publication No. 2004-078136. The plate-like member is slantingly placed on a fulcrum member provided on a substrate, without fixing the plate-like member on the substrate, and the plate-like member is rotated with the fulcrum member made a fulcrum to change the inclination direction of the plate-like member by applying potentials to electrodes arranged around the fulcrum member on the substrate to oppose the plate-like member and thereby a light flux incident to the light reflective area of the plate-like member is reflected with its reflection direction changed. Regulation members provided with cowl-like stoppers at respective upper parts thereof are arranged at corners of the substrate to regulate rotation of the plate-like member.
In an optical deflecting device using a hinge for supporting a plate-like member, a restoration force due to stiffness of the hinge exists, so that the drive voltage becomes relatively high, for example, to a several dozen volt. On the other hand, the optical deflecting device proposed in JP 2004-078136 is constructed such that a plate-like member having a light reflective area does not include a fixing member such as a hinge, and can perform bistable switching of the inclination direction of the plate-like member relatively easily. The electrodes electrically contacting the conductor layer of the plate-like member and the electrodes opposing the plate-like member are divided into two groups with respect to the fulcrum member, and arbitrary potentials are applied to respective groups of the electrodes, and by switching the potentials applied to the electrodes electrically contacting the conductor layer of the plate-like member, the inclination direction of the plate-like member is easily switched. However, the control potentials applied to electrode groups are direct drive voltages, and even when an LSI, etc. are used, if the response time of the plate-like member is equal to or smaller than 5 μsec, a voltage equal to or greater than 10V is necessary. Further, when constituting an image display apparatus by combining an LSI memory with the optical deflecting device, a dedicated high voltage drive device is necessary.